Hacker News Reader

Comment by nojvek | Hacker News Reader

1kg of petrol/gasoline is ~48MJ.

1kg of Lithim-ion battery is ~0.25MJ/kg.

Gasoline is ~192X energy dense compared to Lithium-ion batteries. Li-on is the most popular battery due to its cost and weight.

In terms of weight:

Tesla model Y = ~4,500 lbs.

F-150 lightning = ~6,500 lbs.

Rivian R1T = ~7,000 lbs.

Hummer EV = ~9,000 lbs. ¯\_(ツ)_/¯

Cybertruck = ~5,400 lbs

A human roughly weighs 160lbs (~72kg).

Buying electric trucks IMO is pretty awful for the environment and the road itself. From the energy spent mining the raw materials for that heavy of a battery, to energy spent just moving that battery. The battery weighs more than the passengers.

We're playing stupid games to win stupid prizes in the name of climate change.

View on HN

Except... you can recharge a lithium-ion battery many, many times before you have to replace it. You get to use gasoline one time.

The absolute best efficiency of a gasoline engine is somewhere around 40% efficiency, with most being a lot lower. So your 48MJ number is a lot closer to ~19MJ. So, assuming you can recharge a lithium battery 100 times (most are going to be capable of many times that), you're break even in terms of 'efficiency' of Li-Ion vs. gas.

Even adding in all the additional costs of product, transport, energy generation costs, etc etc, lithium-ion batteries are still better.

In your metaphor the battery would be akin to the gas tank though, rather than the gasoline that fills the tank. I think my gas tank can be emptied and filled more times than a battery and it doesn't lose capacity the more it's used or when it's cold out!

My metaphor works within the confines of equivalency. Battery aging is essentially equivalent to gasoline engine/transmission mileage, as the electric motors and electronics don't meaningfully age unlike gas engines. You can't run a gas engine forever, as eventually maintenance costs will exceed the value of the engine.

Every gas car I'm aware of loses efficiency when it's colder outside. It's not as drastic as an EV, but it definitely exists. Also, gas engines tend to get slightly less efficient as they age, just as components begin to have higher friction, increased wear, worse tolerances, etc.

All my cars had worse mileage in winter.

Not enough for me to notice. I have a route that I can barely do twice without filling up be it summer or winter.

Another way of putting it -- To drive 50,000 miles, a Ford F150 or similar has to consume ~8,500 kgs of gasoline:

> 50,000 miles / 20 mpg * (3.4 kg/gal)

The Cybertruck Battery weighs ~1,400 kgs, and probably lasts at least 100K miles even with poor charging practices

So you would have to compare 1,400kgs of Lithium with at least 17,000 kgs of gasoline over the lifetime of the vehicle.

If you want to be totally fair, you could include your car's share of the weight of fuels used in the electric grid. However, even charging from a fairly dirty grid is more efficient than an ICE, so this wouldn't change things much.

Except... you can recharge a lithium-ion battery many, many times before you have to replace it.

Additionally, we can already recycle it over 90%

If your local electrical grid is powered by oil fired power stations that are so bad that they have similar efficiency to a car engine then this comparison might make some sense. For the other 99.99% of us, it makes none.

I say this very sparingly: this may be one of the worst "numbers-based" comments I've ever read on Hacker News. Typically, such comments don't leave out the critical fact: _you can't reuse gasoline like a battery_.

It's disappointing to see this. Is this kind of comment the result of activism? We typically do much better on HN.

Weight ratio is definitely an issue, but what I want to know is what it will carry. They call it a truck, but is it? Practical truck buyers will want to know upfront if it will carry a full sheet of plywood and how convenient it is to load and unload. If it doesn’t improve upon the current experience, its just an expensive status symbol.

Weight of Cybertruck per the very page associated with this post: 6,843 lbs — but your point still stands.

And then burning coal to charge the batteries.... But these cars are electric!

No coal on my grid (well a tiny amount sometimes but it is being phased out)

https://electricityproduction.uk/in/scotland/

Another thing I’d like to add is that even burning coal it will still break even and deliver less emissions over the lifetime of the vehicle:

> If they drive in Poland, where 90% of the electricity comes from burning coal, then yes, it will take 100,000 kilometers or more to reach parity with a conventional gasoline-powered car.

https://cleantechnica.com/2022/01/21/unpacking-the-electric-...

Even with coal, power plants are much much more efficient than ICEs at converting fuel to energy:

https://www.motortrend.com/news/evs-more-efficient-than-inte...

The US Grid is an 18% coal mix...

... and no new coal plants are being fired to support electric vehicles.

Coal turbines at scale are efficient when compared to thousands of internal combustion engines.

Combine that efficiency with scrubbers and lined waste retention ponds for any plant built in the last 50 years.

It's also not an either/or; A person buying an electric car can vote, support, or install (or offset credit) renewables.

Reply on news.ycombinator.com